v0.3.0-beta.7

This is a prerelease in-development version of the upcoming v0.3.0 release.
Andromeda is now available as AppImage for Linux and as single file executables for Windows, macOS and Linux.

It consists for now out of:

• a first very basic GUI (for now without browser with workaround buttons) which can install, update and start (some) games (now with notifications)
• caches installers and reuses already downloaded files
• uses "unzip" on linux systems for some installers, which otherwise wouldn't install (e.g. State of Mind)
• internal code restructuring
• improve handling of aborted downloads
• settings window where gamepath can be provided
• terminal output of games in Andromeda

This prerelease focusses on linux support, but most functionality should work on windows as well.
Windows and macOS support will become better in future releases.

Caution: Since Beta 3 this program uses a different database (the old one was really problematic for windows builds), so old savefiles can not be used.

I didn't really stick to the beta concept, because there were some nasty bugs in the last version and the GUI was much too complex so I completely lost motivation to try and solve them...
I then found Avalonia.FuncUI and it made writing the UI much more fun and less complex. I therefore migrated the whole GUI code to Avalonia.FuncUI for this release.

As far as I saw everything works again. I will test it for a limited time and then I hopefully can finally release this bad boy as v0.3.0 and work on top of that. And I hopefully make the releases smaller and more frequent...

In Beta6 there were a few bugs with displaying stuff. They are fixed in this version.